A technique of spatially modulating illumination light can be cited as an example of a technique of performing super-resolution of an observation object such as a biological specimen. For example, the technique of spatially modulating illumination light is described in Japanese Patent Application Laid-Open No. 11-242189 (Patent Document 1), U.S. Reissued Patent No. 38307 (Patent Document 2), W. Lukosz, “Optical systems with resolving powers exceeding the classical limit. II”, Journal of the Optical Society of America, Vol. 37, PP. 932, 1967 (Non-Patent Document 1), and W. Lukosz and M. Marchand, Opt. Acta. 10, 241, 1963 (Non-Patent Document 2).
In these techniques, a spatial frequency of a structure of the observation object is modulated with the spatially modulated illumination light, and information on the high spatial-frequency exceeding a resolution limit is caused to contribute to image formation of a microscope optical system. However, in order to observe a super-resolution image, it is necessary to demodulate a modulated image of the observation object (modulated image). The demodulation method is mainly fallen into optical demodulation (see Non-Patent Document 1 and 2) and computing demodulation (see Patent Documents 1 and 2). The optical demodulation is realized by re-modulation of the modulated image with a spatial modulation element such as a diffraction grating.
Patent Document 1: Japanese Patent Application Laid-Open No. 11-242189
Patent Document 2: U.S. Reissued Patent No. 38307
Non-Patent Document 1: W. Lukosz, “Optical systems with resolving powers exceeding the classical limit. II”, Journal of the Optical Society of America, Vol. 37, PP. 932, 1967
Non-Patent Document 2: W. Lukosz and M. Marchand, Opt. Acta. 10, 241, 1963
However, the computing demodulation takes time because of complicated arithmetic processing, and the observation object is hardly observed in real time. On the other hand, the optical demodulation does not take much time because of the use of the spatial modulation element such as a diffraction grating. However, because demodulation accuracy depends on shape accuracy and arrangement accuracy of the spatial modulation element, a good super-resolution image is hardly obtained.
For example, in the demodulation method (optical demodulation) described in Non-Patent Document 2, an optical path for the modulation and an optical path for the demodulation are provided in parallel, and different portions of the common diffraction grating are used in the modulation and the demodulation, thereby improving the problem of the arrangement accuracy. However, there exits a problem that a pupil of the optical system relating to the modulation and a pupil of the optical system relating to the demodulation cannot be conjugated, and therefore an observation field is extremely narrowed.
There is also a demand that both super-resolution observation and normal, simple fluorescence observation are performed without rearranging the observation object in microscopes.
In view of the foregoing, the problem to be solved by the invention is to provide a super-resolution microscope apparatus that can be switched to a normal fluorescence microscope.